As is known, the pressure at which a typical fluid distribution system supplies fluid may vary according to the demands placed on the system, the climate, the source of the supply, and/or other factors. However, most end-user facilities equipped with fluid appliances such as, for example, furnaces, and ovens, require the fluid to be delivered in accordance with predetermined pressure parameters. Therefore, pressure regulators are commonly employed to control the pressure in the system downstream of the regulator while matching a downstream flow demand.
Pressure regulators are typically used to regulate the pressure of a fluid to a substantially constant value. Specifically, a pressure regulator has an inlet that typically receives a supply fluid at a relatively high pressure and provides a relatively lower and substantially constant pressure at an outlet. To regulate the downstream pressure, pressure regulators commonly include a sensing element or diaphragm to sense an outlet pressure in fluid communication with a downstream pressure.
When purchasing a pressure regulator, a customer needs to size the pressure regulator to meet a desired capacity at process conditions representing the full range of required pressures and flow rates which the fluid distribution system could experience. When, however, a perfectly-sized pressure regulator does not exist (i.e., the available sizes do not exactly match up with the size needed to provide the desired capacity), as is almost always the case, the customer must choose the pressure regulator corresponding to the next size up. In other words, the customer must select a larger pressure regulator than necessary. As an example, a pressure regulator having a 2″ body may be too small to meet the desired capacity, and a pressure regulator having a 3″ body may be larger than necessary, but the customer must still purchase the pressure regulator having the 3″ body.
While the larger pressure regulator may meet the desired capacity at worst-case conditions, larger pressure regulators create the potential for greater leakage in a failure situation. This also means more expensive relief capabilities. Because pressure in the system in excess of a predetermined range or threshold can damage the components of a pressure regulator, most systems that employ pressure regulators also include a pressure relief valve located downstream of the regulator to prevent the pressure in the pressure regulator from exceeding this predetermined range or threshold. However, because pressure relief valves are sized based on the wide open flow capacity at the worst-case condition for the upstream pressure regulator, and because pressure relief valves are expensive, employing larger pressure regulators than truly necessary leads the use of larger pressure relief valves than necessary, which leads to unnecessary, and in some cases quite significant, costs for the customer.
In an attempt to limit the potential for leakage and lessen the cost of accompanying relief capabilities, customers have in the past utilized restriction collars or reduced the size of the valve port between the inlet and the outlet, thereby limiting the maximum flow through the regulator (i.e., reducing the flow capacity of the regulator) as much as possible while still meeting the desired capacity. However, these solutions, while effective, require a greater than insignificant amount of design work, testing, and iteration, which is both costly and time-consuming.